This invention relates to network devices, and more particularly, to network devices such as data switches and routers.
Telecommunications networks transmit a large amount of data between various parties, such as businesses, governmental agencies and universities everyday. The increased dependence of various sectors of society on such networks can result in significant disruptions in case of an outage. Mitigation of network downtime is a constant battle for service providers. In particular, service providers strive to minimize network outages due to equipment (i.e., hardware) and all too common software failures.
Traditional networks can experience outages for a variety of reasons. Service providers not only incur downtime due to failures, but also incur downtime for upgrades to deploy new or improved software and hardware, or to deploy software or hardware fixes or patches to deal with particular network problems. A network outage can also occur after an upgrade has been installed if the upgrade itself includes undetected problems or if the upgrade causes other software or hardware to have problems. Downtime may also occur unexpectedly days after an upgrade due to lurking software or hardware incompatibilities. Such outages can result in significant loss of productivity and financial losses.
The present invention provides a network device, such as a switch or a router or a hybrid switch-router, that ensures high availability and reliability, minimizes the probability of a network outage and allows for reliable and efficient software and hardware upgrades. The computer network device includes a plurality of subsystems for transmitting data between a receiving port and a transmitting port. An internal control device that is in communication with these subsystems manages the internal resources and events within the device. An external control device that is in communication with the internal control device and the subsystems manages operations relating to interfacing of the network device with an external environment. The internal control device and the external control device have separate processor subsystems, and hence do not need to share processing cycles.
In a related aspect, a network device of the invention includes a data plane for transmitting data between a receiving port and a transmitting port, and a control plane in communication with the data plane for managing the internal components and events and external network protocols and events and for interfacing the device with an external environment. The term external environment as used herein refers to other devices with which a network device communicates. Such external devices can, for example, include switches, routers, computer systems, etc. The control plane includes an internal control device for managing the internal resources and events within the device and an external control device for managing operations relating to interfacing of the network device with an external environment. The internal control device and the external control device include separate processor subsystems, and hence do not need to share processing cycles. This allows a more reliable operation of the network device, as described in more detail below.
In one aspect of the invention, the network device can include a message based communication bus, such as Ethernet, token ring, or any proprietary bus, for providing communication between the internal control device and the external control device, and also between the internal and external control devices and subsystems within the data plane. Such a communication bus can also allow the subsystems within the data plane to communication with each other.
In one embodiment, the communication bus includes an Ethernet bus and the internal control device employs an Ethernet switch to communicate with other devices and subsystems of the network device. The internal control device communicates with various subsystems of the network device in order to manage the internal resources of the device and internal events within the device. For example, the internal control device can detect faults and initiate fail-overs to redundant hardware or restart software processes, detect newly added hardware within the device, configure and re-configure hardware and software within the device, upgrade and downgrade software processes, provide fault analysis of selected subsystems of the network device, and gather data relevant to network accounting and statistics.
The Ethernet switch also allows the external control device to communicate with the various subsystems in the data plane to receive network protocol control payloads, for example, Private Network-to-Network Interface (PNNI), Open Shortest Path First (OSPF), and Border Gateway Protocol (BGP), to allow the external control device to set up and tear down network connections through the device (e.g., virtual circuits and virtual paths). The external control device also monitors selected attributes of the external environment with which the network device is interfaced. For example, when the external environment is a network of computers, the external control device monitors the topology/configuration of the external network, and the external network traffic.
In another aspect of the invention, the data received and transmitted by the network device of the invention is optical data formatted as Synchronous Optical Network (SONET) frames. Ethernet interfaces are also prevalent. The data plane receives the SONET frames, transforms them into cells or packets according to a particular network protocol, for example, Asynchronous Transfer Mode (ATM), Internet Protocol (IP), Frame Relay (FR) or Multi-Protocol Label Switching (MPLS), re-assembles the cells or packet into SONET frames, and transmits the re-assembled SONET frames to selected destinations in the external environment.
In another aspect of the invention, the data received and transmitted by the network device of the invention is electrical data provided on an Ethernet bus. The data plane receives data from the Ethernet bus, transforms it into cells or packets according to a particular network protocol, for example, ATM, IP, FR, or MPLS, re-assembles the data, and transmits the data to selected destinations in an external environment.
In one aspect of the invention, the data plane includes a physical connection subsystem that includes an interface logic for receiving a payload of data from the physical layer, e.g., SONET interface logic receives SONET frames carried on an optical fiber. The physical connection subsystem provides limited processing of the received payload before transmitting it to a cross-connect subsystem. For example, the physical connection subsystem can parse the location of the user data within each SONET frame.
The cross-connect subsystem routes or switches the data received from the physical connection subsystem to a forwarding subsystem. The forwarding subsystem transforms the data into cells, frames or packets based on the network protocol employed. For example, the forwarding subsystem can transform the SONET frames or Ethernet data into a stream of ATM cells. Alternatively, the forwarding subsystem can transform SONET frames or Ethernet data into a stream of Internet Protocol (IP) or Multi-Protocol Label Switching (MPLS) packets. The forwarding subsystem employs an interface to communicate with a switching fabric that receives the cells, frames or the packets and routes or switches them to a number of egress subsystems.
The egress subsystems can include forwarding subsystems in communication with physical connection subsystems via one or more cross-connect subsystems. These egress subsystems re-assemble the cells, frames or packets into, for example, SONET frames or Ethernet data, and transmit the frames or data to designated destinations in the external environment.
Illustrative embodiments of the network device of the invention will be described below with reference to the following drawings.